A technique that is well known for making a thruster combustion chamber consists in separately making a tubular structure or shell constituting a thruster body and end walls which are attached to the ends of the tubular structure. One of the end walls, the rear end wall, leaves a passage for combustion gases leading to a nozzle. The tubular structure is commonly made of composite material, using a filament-winding technique, with the tubular structure being required to withstand the high pressures that are generated in the combustion chamber. The end walls may likewise be made of composite material, but they also be made of metal, e.g. titanium. The connection between the tubular structure and an end wall includes mechanical connection means suitable for withstanding the pressures generated in the chamber and at least one sealing gasket that prevents any gas from flowing between the tubular structure and the end wall.
A known device for providing a sealed connection between the tubular structure and the rear end wall of the combustion chamber of a thruster is shown diagrammatically in FIG. 1. The tubular structure 1 of composite material and the metal rear end wall 2 are assembled together by means of screws 3. The end wall 2 has a ring-shaped peripheral portion 2a engaged inside the tubular structure and receiving the screws 3 that pass through the tubular structure. The screws 3 are disposed in one or more circumferential rows. An O-ring or toroidal gasket 5 is compressed between the portion 2a of the end wall and an annular gasket bearing member 6 constituted by metal coating over a portion of the inside surface of the tubular structure 1. The tubular structure 1 and the end wall 2 are provided with respective internal thermal protection coatings 7 and 8. Thermal protection coating 7 is made of rubber and is adhered to the inside faces of the tubular structure and the gasket bearing member 6.
This known solution suffers from several drawbacks. It is necessary to tighten hard screws 3 in the circumferential row closest to the gasket 6 in order to ensure that the gasket is sufficiently compressed even in the event of the end wall deforming, e.g. under the effect of high internal pressure inside the chamber. In addition, the screws suffer shear, bending, and lateral hammering stresses. The internal pressure inside the chamber gives rise to very large axial forces on the end wall and to correspondingly large transverse forces across the screw threads. However, lateral hammering stresses on the screw threads along a transversal axis must be avoided, and are in fact ruled out by U.S. aviation standard MIL STD 1515A.
In document U.S. Pat. No. 4,766,726, a combustion chamber of a solid fuel thruster is made up of two portions, a front portion and a rear portion, which are assembled by means of an annular coupling element. The connection between the coupling element and each of the tubular structures of the front and rear portions of the chamber is provided by means of smooth-walled radial studs and wedges which, on screwing, exert shear forces on the studs. As a result, the studs restrain not only axially but also radially so as to maintain the compressed state of a sealing O-ring placed between each of the tubular structures and the coupling element. The fixing elements are thus not screws, but smooth studs that are subjected to shear stresses. Nevertheless, a drawback of that solution lies in that the shear force exerted on the studs must be very high in order to avoid any relative radial displacement between the assembled parts and a consequent sealing loss through a release of compression on the O-ring gasket, particularly in the event of thermally-induced dimensional variations. A construction similar to that of patent U.S. Pat. No. 4,766,726 is described in the publication AVIATION WEEK AND SPACE TECHNOLOGY, 9, Feb. 1989, NEW YORK US, pages 119-123, DORNHEIM `Thiokol begins full-diameter tests of redesigned SRB field joint`.